Ammoxidation catalysts containing germanium to produce high yields of acrylonitrile

ABSTRACT

A catalyst having the atomic ratios set forth in the empirical formula below: 
     
         A.sub.a B.sub.b C.sub.c Ge.sub.d Bi.sub.e Mo.sub.12 O.sub.x 
    
     where 
     A=two or more of alkali metals, In and Tl 
     B=one or more of Mg, Mn, Ni, Co, Ca, Fe, Ce, Sm, Cr, Sb, and W; preferably B equals the combination of Fe and at least one element selected from the group consisting of Ni and Co and at least one element selected from the group consisting of Mg, Mn, Ca, Ce, Sn, Cr, Sb, and W 
     C=one or more of Pb, Eu, B, Sn, Te and Cu 
     a=0.05 to 5.0 
     b=5 to 12 
     c=0 to 5.0 
     d=0.1 to 2.0 
     e=0.1 to 2.0 
     x=the number of oxygen atoms required to satisfy the valency requirements of the other elements and 
     b&gt;a+c.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of U.S. Ser. No. 08/432,329filed May 1, 1995.

FIELD OF THE INVENTION

The present invention is directed to an improved ammoxidation catalystfor use in the manufacture of acrylonitrile. In particular, the presentinvention is directed to an improved ammoxidation catalyst containinggermanium as an essential element and a combination of at least twoalkali metals for the production of acrylonitrile by the ammoxidation ofpropylene.

The ammoxidation of propylene to acrylonitrile using a fluid bedcatalyst is a well known commercial process referred to in the industryas the Sohio Acrylonitrile Process. The process comprises contactingpropylene over a catalyst in a fluid bed reactor at an elevatedtemperature in the presence of ammonia and air. High yields ofacrylonitrile have been obtained utilizing this process.

A number of very desirable ammoxidation catalysts are known whichrepresent the base catalyst utilized in the practice of the presentinvention. These catalysts have been used not only to produceacrylonitrile but also methacrylonitrile. Examples of patents whichdisclose catalysts suitable for the ammoxidation of propylene toacrylonitrile in a fluid bed reactor include U.S. Pat. Nos. 4,190,556;4,162,234; 4,001,317; 4,001,317 and 5,093,299. Each of these patents isassigned to the assignee of the instant application.

While current commercial catalysts produce desirable results in thecommercial production of acrylonitrile, improvement is always beingsought. The present invention is directed to an improved ammoxidationcatalyst containing at least two alkali metals and germanium as anessential element for the production of acrylonitrile.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ammoxidationcatalyst useful in the manufacture of acrylonitrile.

It is another object of the present invention to provide a novel processfor the manufacture of acrylonitrile utilizing a fluid bed ammoxidationcatalyst.

It is still another object of the present invention to provide a novelmethod of preparing an ammoxidation catalyst useful for the productionof acrylonitrile.

Additional objects and advantages of the invention are set forth in partin the description which follows and, in part will be obvious from thedescription or may be learned by the practice of the invention. Theobjects and advantages of the invention may be realized and attained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

To achieve the foregoing objects and advantages as set forth above, thecatalyst of the present invention has the atomic ratios described by theempirical formula set forth below:

    A.sub.a B.sub.b C.sub.c Ge.sub.d Bi.sub.e Mo.sub.12 O.sub.x

where

A=two or more of alkali metals, In and Tl, preferably Li, K and Cs

B=one or more of Mg, Mn, Ni, Co, Ca, Fe, Ce, Sm, Cr, Sb, and W;preferably B equals the combination of Fe and at least one elementselected from the group consisting of Ni and Co and at least one elementselected from the group consisting of Mg, Mn, Ca, Ce, Sn, Cr, Sb, and W

C=one or more of Pb, Eu, B, Sn, Te and Cu;

a=0.05 to 5.0

b=5 to 12

c=0 to 5.0

d=0.1 to 2.0

e=0.1 to 2.0

x=the number of oxygen required to satisfy the valency requirements ofthe other elements present, and

b>a+c.

It is also an additional object of the present invention to provide aprocess for the preparation of acrylonitrile or methacrylonitrile by thereaction of propylene or isobutylene, molecular oxygen and ammonia at atemperature of between 200° C. to about 600° C. in the presence of acatalyst, the improvement comprising using a catalyst having the atomicratios described by the empirical formula set forth below:

    A.sub.a B.sub.b C.sub.c Ge.sub.d Bi.sub.e Mo.sub.12O.sub.x

where

A=two or more of alkali metals, In and Tl, preferably Li, K and Cs

B=one or more of Mg, Mn, Ni, Co, Ca, Fe, Ce, Sm, Cr, Sb, and W;preferably B equals the combination of Fe and at least one elementselected from the group consisting of Ni and Co and at least one elementselected from the group consisting of Mg, Mn, Ca, Ce, Sn, Cr, Sb, and W

C=one or more of Pb, Eu, B, Sn, Te and Cu;

a=0.05 to 5.0

b=5 to 12

c=0 to 5.0

d=0.1 to 2.0

e=0.1 to 2.0

x=the number of oxygen required to satisfy the valency requirements ofthe other elements present, and

b>a+c.

In a preferred embodiment of the present invention the catalyst issupported on inert supports selected from the group consisting ofsilica, alumina, zirconia and mixtures thereof. Most preferably thesupport is silica. Typically, the level of the support is usually in therange of 20 to 70 weight percent, preferably the range of the support isbetween 40 to 60 weight percent.

The catalysts of the present invention are prepared by conventionalprocedures taught in the prior art. However, it has been discovered thatonce the catalyst ingredients have been mixed typically in the form ofmetal nitrate solutions and ammonium hepta-molybdate that the catalystperformance may be improved by certain calcination procedures.Accordingly, it is a further object of the present invention to providea procedure for treating the catalyst precursor comprising an aqueousmixture of the metal nitrates and ammonia hepta-molybdate as follows:the catalyst precursor is dried at a temperature of 50° to 300° C. in ahot chamber, the temperature is then increased to a temperature of 200°to 500° C. to remove the nitrates from the catalyst precursor, finally,the catalyst precursor is calcined at a temperature of between 450° to750° C. to produce the resulting catalyst.

Typically, the heat treatment can be done in a reducing environment suchas ammonia, carbon, carbon monoxide, nitrous oxide, or an inertenvironment such as nitrogen, carbon dioxide, steam, etc., or in anoxidizing environment such as air, oxygen, nitrogen dioxide, etc., andtheir combinations. The nitrogen oxide evolved during thede-nitrification can also be passed over the catalyst to improve thecalcination of the catalyst at various stages of the heat treatment.

In a preferred embodiment of the present invention, the amount of Aelement present in the catalyst may range from a=0.05 to 2, preferably0.1 to 2.

In another preferred embodiment of the present invention, the amount ofB element may range from b=6 to 12, preferably 8 to 12.

In still another embodiment of the present invention, C varies from 0.1to 2.

In a further preferred embodiment of the present invention, B equals thecombination of Fe and Ni plus at least one element selected from thegroup consisting of Mg, Mn, Ca, Ce, Sn, Cr, Sb, and W.

In another preferred embodiment of the present invention, B equals thecombination of Fe plus at least one element selected from the groupconsisting of Ni and Co plus at least one element selected from thegroup consisting of Mg, Mn, Ca, Ce, Sb, and W.

In still another preferred embodiment of the present invention, B equalsthe combination of Fe plus Ni plus at least one element selected fromthe group consisting of Mg, Mn, Ca, Ce, Sb, and W.

In a still further preferred embodiment of the present invention, thecatalyst is substantially free of phosphorus.

The reactants, process conditions and other reaction parameters of thereaction are known in the art of ammoxidation of propylene andisobutylene. The conditions, reactors and the like are not substantiallychanged from those disclosed in the art. The temperatures may range fromabout 200° to 600° C. with about 300° to 500° C. being preferred. Thereaction may be conducted in a fluid or fixed bed reactor usingatmospheric, sub-atmospheric or super-atmospheric pressures. Preferably,the reaction is conducted in a fluid bed reactor at atmosphericpressures. The reactant feed rate is normally stated as "WWH" and ismeasured according to the following formula: WWH=weight of olefinfed/weight of catalyst times hours. Typically, the WWH ranges frombetween 0.05 to about 0.25. The following examples are illustrative ofthe claimed invention and are supplied for purposes of illustrationonly.

Specific Examples:

Catalysts containing germanium and catalysts without germanium wereprepared in fluid bed form. All these catalysts contain 40 weightpercent SiO₂. The inlet of the spray drier was 325° C., and the outlettemperature was 145° C. The catalyst was de-nitrified at 290° C. for aperiod of 3 hours followed by 425° C. for 3 hours. Final calcination wasdone in air at 540°-590° C. for 3 hours. The microspheroidal catalystwas placed in a 40 cc fluid bed reactor, and a feed containing a mixtureof NH₃ and N₂ was passed over the catalyst at ˜440° C. for a period of10 minutes. The feed was then changed to a gas mixture containingpropylene, ammonia, oxygen and nitrogen, and the temperature of thereactor was lowered to 410°-420° C. Recovery runs were made after thecatalyst had been on this feed gas for about 20 hours. The followingexamples clearly show the advantage of germanium in the molybdate basedcatalysts:

                                      TABLE I                                     __________________________________________________________________________    Ex. No.  Composition of Catalysts                                                                             % AN Yield                                    __________________________________________________________________________    1 (Comparative)                                                                        Li.sub.0.25 Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 -                                             82.2                                                   Fe.sub.2 Bi.sub.0.75 Ce.sub.0.5 Mo.sub.14.0 O.sub.X                  2        Li.sub.0.25 Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 -                                             82.5                                                   Fe.sub.2 Bi.sub.0.75 Ce.sub.0.5 Mo.sub.14.0 Ge.sub.0.5 O.sub.X       3 (Comparative)                                                                        Li.sub.0.25 Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2               Bi.sub.0.5 Ce.sub.0.5 Mo.sub.13.6 O.sub.X                                                            82.1                                          4        Li.sub.0.25 Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 -                                             82.6                                                   Fe.sub.2 Bi.sub.0.5 Ce.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X        5 (Comparative)                                                                        *Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5               Ce.sub.0.6 Mo.sub.13.6 O.sub.X                                                                       81.5                                          6        Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5                Ce.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                            82.4                                          7        Ge.sub.0.5 Li.sub.0.5 Cs.sub.0.1 K.sub.0.1 Ni.sub.8.7 -                                              82.7                                                   Mg.sub.0 Fe.sub.2 Bi.sub.0.75 Ce.sub.0.5 Mo.sub.13.6 O.sub.X         8        Ge.sub.0.5 Li.sub.0.5 Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 -                                              82.5                                                   Mg.sub.2.5 Fe.sub.2 Bi.sub.0.75 Ce.sub.0.5 Mo.sub.13.6 O.sub.X       9        Ge.sub.0.5 Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2                Bi.sub.0.75 Ce.sub.0.5 Mo.sub.14.0 O.sub.X                                                           82.3                                          __________________________________________________________________________     *Catalyst contains 50% SiO.sub.2 support                                 

Several fixed bed catalysts, supported with 40 weight percent SiO₂, wereprepared with and without germanium. These catalysts were dried in adrying oven at ˜130° C. for ˜24 hours followed by 290° C. heat treatmentfor 3 hours and 425° C. heat treatment for 3 hours. The catalyst wasthen broken into 20 to 35 mesh particles and further calcined at550°-600° C. for a period of 3 hours. The catalyst was then placed in 5cc microreactor at ˜430° C. and evaluated for the ammoxidation ofpropylene to acrylonitrile by feeding a gas mixture containingpropylene, ammonia oxygen, nitrogen and water. All catalysts were testedunder identical conditions. The following examples will show thedistinct advantage of adding germanium to the molybdate based catalysts.

                                      TABLE II                                    __________________________________________________________________________    Ex. No.  Composition of Catalysts                                                                             % AN Yield                                    __________________________________________________________________________    10 (Comparative)                                                                       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5                Ce.sub.0.5 Mo.sub.13.6 O.sub.X                                                                       82.7                                          11       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5                Ce.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                            84.4                                          12       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 -                                                84.2                                                   Bi.sub.0.5 Ce.sub.0.5 Mo.sub.13.8 Ge.sub.0.5 O.sub.X (Ge to AHM)     13       Cs.sub.0.1 K.sub.0.1 Ni.sub.8.7 Fe.sub.2 Bi.sub.0.5 Ce.sub.0.5                Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                                       82.7                                          14       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.75               Ce.sub.0.5 Mo.sub.14.0 Ge.sub.0.5 O.sub.X                                                            83.6                                          15       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5                Ce.sub.0.5 Mo.sub.12.8Ge.sub.0.5 O.sub.X                                                             82.0                                          16       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5                Ce.sub.0.5 Mo.sub.13.2Ge.sub.0.5 W.sub.0.4 O.sub.X                                                   83.8                                          17       Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5                Ce.sub.0.5 Mo.sub.14.1Ge.sub.0.75 O.sub.X                                                            84.0                                          18 (Comparative)                                                                       *Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5               Ce.sub.0.5 Mo.sub.13.6 O.sub.X                                                                       82.1                                          19       *Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5               Ce.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                            82.9                                          20 (Comparative)                                                                       *Cs.sub.0.1 K.sub.0.1 Ni.sub.5.5 Mg.sub.2.2 Fe.sub.2 Mn.sub.1                 Bi.sub.0.5 Cr.sub.0.5 Mo.sub.12.3 O.sub.X                                                            82.0                                          21       *Cs.sub.0.1 K.sub.0.1 Ni.sub.5.5 Mg.sub.2.2 Fe.sub.2 Mn.sub.1                 Bi.sub.0.5 Cr.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                 84.4                                          22       *Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.75              Cr.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                            85.3                                          23       *Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.5               Ce.sub.0.25 Mo.sub.13.6 Ge.sub.0.25 O.sub.X                                                          83.9                                          24       *Cs.sub.0.1 K.sub.0.1 Ni.sub.6.2 Mg.sub.2.5 Fe.sub.2 Bi.sub.0.875              Ce.sub.0.5 Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                           82.6                                          25       *Cs.sub.0.1 K.sub.0.1 Ni.sub.8.7 Fe.sub.2 Bi.sub.1.0 Ce.sub.0.5               Mo.sub.14.4 Ge.sub.0.5 O.sub.X                                                                       84.8                                          26       *Cs.sub.0.1 K.sub.0.1 Ni.sub.8.8 Fe.sub.2 Bi.sub.1.75 Ce.sub.0.5              Mo.sub.14.1 Ge.sub.0.5 O.sub.X                                                                       83.7                                          27       *Cs.sub.0.1 K.sub.0.1 Ni.sub.8.7 Fe.sub.2 Bi.sub.0.5 Ce.sub.0.5               Mo.sub.13.6 Ge.sub.0.5 O.sub.X                                                                       83.7                                          __________________________________________________________________________     *Contains 50 wt% SiO.sub.2                                               

The foregoing description of the preferred embodiments of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and obviously many modifications and variations arepossible in light of the above teaching. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application to thereby enable others skilled in the art tobest utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the claimsappended hereto.

What is claimed as our invention is:
 1. A catalyst having the atomicratios set forth in the empirical formula below:

    A.sub.a B.sub.b C.sub.c Ge.sub.d Bi.sub.e Mo.sub.12 O.sub.x

where A=two or more of alkali metals, In and Tl B=the combination of Feplus at least one element selected from the group consisting of Ni andCo plus at least one element selected from the group consisting of Mg,Mn, Ca, Ce, Sn, Cr, Sb, and W C=one or more of Pb, Eu, B, Sn, Te, and Cua=0.05 to 5.0 b=5 to 12 c=0 to 5.0 d=0.1 to 2.0 e=0.1 to 2.0 x=thenumber of oxygen atoms required to satisfy the valency requirements ofthe other elements and b>a+c.
 2. The catalyst of claim 1 where A equalsat least two elements selected from the group consisting of Li, K, andCs.
 3. The catalyst of claim 1 wherein a can range from 0.05 to
 2. 4.The catalyst of claim 3 wherein a can range from 0.1 to
 2. 5. Thecatalyst of claim 1 wherein b can range from about 6 to
 12. 6. Thecatalyst of claim 1 wherein the catalyst is substantially free ofphosphorous.
 7. The catalyst of claim 1 wherein c can range from 0.1 to2.
 8. The catalyst of claim 1 wherein B equals the combination of Feplus Ni and at least one element selected from the group consisting ofMg, Mn, Ca, Ce, Sn, Cr, Sb, and W.
 9. The catalyst of claim 8 whereinthe inert support is selected from the group consisting of silica,zirconia, alumina and mixtures thereof.
 10. The catalyst of claim 8wherein the inert support is present in the range of 20 to 70 weightpercent.
 11. The catalyst of claim 10 wherein the inert support ispresent in the range of 40 to 60 weight percent.
 12. The process offabricating the catalyst of claim 1 comprising forming an aqueousmixture of metal nitrates and ammonium hepta-molybdate to form acatalyst precursor, drying said precursor at an elevated temperature,heating said dried precursor to remove the nitrates and calcining saiddenitrified precursor to produce the catalyst wherein the improvementcomprising calcining said denitrified catalyst at a temperature in therange of about 450° C. to 750° C.